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81.
为了有效去除低浓度含镍络合废水中的镍离子(Ni~(2+)),探究影响Ni~(2+)去除效果的因素和方法,通过改变低浓度溶液中沉淀pH值、H_2O_2与Fe~(2+)摩尔比、H_2O_2投加量、初始pH值和反应时间,基于UV/Fenton法,研究了以上各因素对Ni~(2+)去除效果的影响及机理;同时比较UV/Fenton法与Fenton法对Ni~(2+)的去除效果,自配含有典型络合剂的镀镍模拟废水,酒石酸∶柠檬酸∶乙二胺四乙酸∶镍(摩尔比)为1.5∶2∶1.5∶1,Ni~(2+)含量5 mg/L,pH 4.0;光催化实验在光化学反应仪中进行,反应系统由循环水冷却,维持温度在(32±2)℃,光强度为12.7 mW/cm~2。50 mL的石英管中依次加入模拟络合镍废水和一定量的Fenton试剂,100 W中压汞灯光照下进行连续磁力搅拌;光照一定时间后,NaOH调节pH至11.0,离心后取上清液测定镍含量,测定方法采用火焰原子吸收分光光度计。结果显示,UV/Fenton法去除Ni~(2+)的最佳反应条件为初始pH值2.6左右,H_2O_2∶Fe~(2+)(摩尔比)为3∶1,H_2O_2投加量为3 mmol/L,反应时间为1 h,沉淀pH值为11.0,Ni~(2+)去除率可达98%以上。研究表明,增大沉淀pH值、合理控制H_2O_2浓度、增加反应时间,可提高低浓度镍络合物中Ni~(2+)的去除效果;相较于单一Fenton法,采用UV/Fenton法可更好的去除低浓度镍络合物中的Ni~(2+)。 相似文献
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84.
Li-Ping Hu Fan-Zhen Meng Shao-Hui Wang Xiao-Lei Sui Wei Li Yu-Xia Wei Jian-Lei Sun Zhen-Xian Zhang 《Scientia Horticulturae》2009
Levels of carbohydrates and activities of metabolic enzymes were examined in leaves (source), phloem sap (flow) and mesocarp tissues (sink) in the course of cucumber (Cucumis sativus L.) fruit development, from 2 days before anthesis to 20 days after anthesis. While total sugar levels increased in all the three sampling organs, starch levels declined in leaves and mesocarp tissues as fruit development progressed. Glucose and fructose were the primary contributors to the soluble sugar pools in mature leaves. Stachyose was found as the most important component of the phloem sap extracts, followed by sucrose and raffinose. However, the primary sugars accumulated in mesocarp tissues were glucose and fructose, not stachyose or sucrose. Activities of sucrose synthesizing enzymes (sucrose phosphate synthase plus sucrose synthase in the synthesizing direction) exceeded that of sucrose degrading enzymes (acid invertase, neutral invertase plus sucrose synthase in the degrading direction) in leaves, which might cause a sucrose pool utilized in raffinose and stachyose biosynthesis. While alkaline a-galactosidase form I activity declined, stachyose synthase activity showed a rapid increase until 12 days after anthesis and only subsequently decreased in leaves. Activities of sucrose degrading enzymes were always much higher than that of sucrose synthesizing enzymes in mesocarp tissues. Thus, sucrose accumulation could not occur in mesocarp tissues. While stachyose synthase activity steadily decreased, alkaline a-galactosidase form I activity showed a moderate increase before decrease in mesocarp tissues. The relationship between levels of soluble sugars and activities of relative enzymes was also discussed. 相似文献
85.
《Communications in Soil Science and Plant Analysis》2012,43(10):1237-1244
To investigate the distribution and dynamics of phosphorus (P) in soils for environmental protection and agronomical usage, 31P nuclear magnetic resonance spectroscopy (31P NMR) was used to characterize the contents and chemical properties of P in sewage sludge from 13 wastewater treatment plants in Shanghai. The samples were extracted with 0.25 M sodium hydroxide (NaOH) / 0.05 M sodium ethylenediamietetraacetic acid (Na2EDTA) in ratio of 1:20 (w/v). Total P recovery in the extract ranged from 91 to 116% when compared to traditional chemical methods. The dominant forms of P in all samples were inorganic orthophosphates and orthophosphates monoesters. Orthophosphate diesters and pyrophosphates were present in only two and four samples, respectively. This study provides detailed information on the distribution, contents, and chemical properties of P in sewage sludge that may be of value in the utilization of sewage sludge for agronomic purposes. 相似文献
86.
《Communications in Soil Science and Plant Analysis》2012,43(7):661-668
Abstract Two contrasting soils were extracted with 0.05 M EDTA in 1 M CH3 COONH4 at pH 6, before and after incubation for 4 weeks at constant (10, 20 or 30°C) or fluctuating (10/30, mean 20°C) temperatures. Less copper was extracted from soils which were incubated at fluctuating temperature than from those maintained at a constant 20 C. Where incubation temperature was constant, extractable copper increased or decreased with increasing temperature depending on the soil and how it was treated. Recovery of added copper was low initially but increased during the incubation. Maximum recovery was associated with low incubation temperature in one soil, but high temperature in the other. The amounts of copper extracted were slightly increased by γ‐irradiation of the soils. Extractable copper was also increased by increasing the temperature at which the extraction was performed. 相似文献
87.
《Communications in Soil Science and Plant Analysis》2012,43(13-14):1963-1978
Abstract: The fraction distributions of heavy metals have attracted more attention because of the relationship between the toxicity and their speciation. Heavy‐metal fraction distributions in soil contaminated with mine tailings (soil A) and in soil irrigated with mine wastewater (soil B), before and after treatment with disodium ethylenediaminetetraacetic acid (EDTA), were analyzed with Tessier's sequential extraction procedures. The total contents of lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) exceeded the maximum permissible levels by 5.1, 33.3, 3.1, and 8.0 times in soil A and by 2.6, 12.0, 0.2, and 1.9 times in soil B, respectively. The results showed that both soils had high levels of heavy‐metal pollution. Although the fractions were found in different distribution before extraction, the residual fraction was found to be the predominant fraction of the four heavy metals. There was a small amount of exchangeable fraction of heavy metals in both contaminated soils. Furthermore, in this study, the extraction efficiencies of Pb, Cd, and Cu were higher than those of Zn. After extraction, the concentrations of exchangeable Pb, Cd, Cu, and Zn increased 84.7 mg·kg?1, 0.3 mg·kg?1, 4.1 mg·kg?1, and 39.9 mg·kg?1 in soil A and 48.7 mg·kg?1, 0.6 mg·kg?1, 2.7 mg·kg?1, and 44.1 mg·kg?1 in soil B, respectively. The concentrations of carbonate, iron and manganese oxides, organic matter, and residue of heavy metals decreased. This implies that EDTA increased metal mobility and bioavailability and may lead to groundwater contamination. 相似文献
88.
Chemical properties and reactivity of manganese chelates and complexes in solution and soils 下载免费PDF全文
Commercial fertilizers containing synthetic manganese (Mn) chelates and complexes are currently used to alleviate Mn deficiency in crops. However, studies conducted on Mn sources in order to evaluate their behavior maintaining Mn soluble in nutrient solution and soil have not been done. In this work, representative commercial Mn fertilizers based on chelates and complexes were characterized and their chemical stability in solution and interaction with soils has been evaluated. Fertilizers studied were two ethylene diamine tetraacetic acid (EDTA) Mn chelates, one N‐(1,2‐dicarboxyethyl)‐D,L‐aspartic acid (IDHA) Mn chelate, two lignosulfonates, one carboxylate, one fulvate, one gluconate, and one heptagluconate‐based Mn complex. Characterization consisted of the determination of the soluble and chelated or complexed Mn, and the ligand identification by nuclear‐magnetic resonance (NMR). Stability study included batch experiments in Ca solution at different pH and three batch experiments with soil comparing with MnSO4. Results indicate that most of the Mn fertilizers comply with the declared “soluble and chelated or complexed” metal content. At a usual pH range of calcareous soils (7.5–8.5), both chelates and complexes maintain more Mn in solution than MnSO4 in the presence of Ca. Several factors affect the Mn remaining in solution after the interaction with the soil, especially, the soil‐to‐solution ratio. All chelates and complexes are better alternatives to the use of MnSO4 in agronomical practices such as fertigation and soil application. Mn‐IDHA as chelate and Mn‐HGl or Mn‐Carb as complexes can be efficient, economical, and environmental friendly fertilizers for foliar application and hydroponic cultures. In soil application, Mn‐EDTA or Mn‐LS would be the best options. In this case, lignosulfonic acid represents a sustainable and low‐cost solution. 相似文献
89.
通过盆栽试验,研究了Pb及Pb-Cd复合污染土壤添加EDTA(乙二胺四乙酸)对小藜生长和转运、富集Pb、Cd的影响。结果表明,高浓度的EDTA对小藜的生长有抑制作用,Pb及Pb-Cd复合处理下EDTA最佳添加浓度均为2.5 mmol·kg^-1,此时小藜对Pb的转运系数达2.66和2.41,富集系数达1.51和1.82,分别比对照提高554%和493%、8 431%和2 367%;对Cd的转运系数达1.87和3.47,富集系数达1.78和10.8,分别比对照提高165%和355%、77%和283%。2.5 mmol·kg^-1EDTA辅助小藜修复Pb-Cd复合污染土壤的效果优于修复Pb污染土壤的效果。 相似文献
90.
建立了EDTA滴定法测定饲料中钙含量不确定度评定的数学模型,分析了检测过程中不确定度的来源并计算了各不确定度分量,并得出合成标准不确定度和扩展不确定度。在产蛋鸡配合饲料钙含量的测定中,钙含量为4.00%,其扩展不确定度为0.040%,K=2。影响钙含量测量结果不确定度的最大因素是重复性实验的不确定度。 相似文献